Independent power control of processing cores

ABSTRACT

Independent power control of two or more processing cores. More particularly, at least one embodiment of the invention pertains to a technique to place at least one processing core in a power state without coordinating with the power state of one or more other processing cores.

PRIORITY

This is a continuation of application Ser. No. 11/555,609, filed on Nov.1, 2006, entitled “Independent power control of processing cores,” andassigned to the corporate assignee of the present invention andincorporated herein by reference.

BACKGROUND

1. Field

The present disclosure pertains to the field of computing and computersystems, and, more specifically, to the field of power control ofmicroprocessors.

2. Background

Some computing systems and microprocessors may contain multipleprocessing elements, or “cores”, to execute instructions of a programand perform some function in response thereto. For example, multipleprocessing cores may exist on the same processor die. Alternatively orconjunctively, some computer systems may include multiple processors,each having one or more processing cores. Moreover, some computingsystems and microprocessors may be able to control power consumption ofone or more processing cores by placing the cores in various powerstates, which may be defined according to a power specification, such asACPI (defined) or some other specification.

However, processing systems and microprocessors may not be able tocontrol the power states of each processing core independently, but mustcoordinate a power state changes among the various cores present in thesystem or processor by using such techniques as polling the power stateof other processing cores or otherwise detecting the power state ofother cores in some way. Accordingly, the power states of a processingcore may be dependent upon at least one other processing core in acomputing system or processor.

Because some processing systems or processors may rely on the processingstates of one or more cores to control the processing state of aparticular core, the system or processor may require additional controlcircuitry to change a core's power state. Furthermore, polling orotherwise detecting power states of other processing cores before beingable to change the power state of a particular processing core mayrequire additional time before the core's processor state may bechanged, which can degrade processing performance. Ironically, theadditional circuitry needed to coordinate a power state change of aprocessing core with one or more other processing cores may cause theprocessor or system to draw more power, thereby at least partiallyoffsetting the power consumption reduction of reducing a power statechange intended to conserve power.

BRIEF DESCRIPTION OF THE FIGURES

The present invention is illustrated by way of example and notlimitation in the accompanying figures.

FIG. 1 illustrates a multi-core processor, in which at least oneembodiment of the invention may be used.

FIG. 2 illustrates a processor core and uncore logic in which oneembodiment of the invention may be used.

FIG. 3 illustrates power control logic according to one embodiment ofthe invention.

FIG. 4 is a flow diagram illustrating operations used in changing powerstates of at least one processing core according to one embodiment ofthe invention.

FIG. 5 illustrates a shared-bus computing system in which at least oneembodiment of the invention may be used.

FIG. 6 illustrates a point-to-point computing system in which at leastone embodiment of the invention may be used.

DETAILED DESCRIPTION

Embodiments of the invention relate to computer systems. Moreparticularly, some embodiments of the invention relate to a technique tocontrol power consumption of two or more processing cores or portions ofcores independently of each other. At least one embodiment of theinvention enables at least one processing core to enter a number ofpower states without consideration to the power state at least one otherprocessing core within the same processor or computing system. At leastone embodiment, enables independent power control of circuits orfunctional blocks within one or more cores.

At least one embodiment of the invention may control power consumptionof one or more cores by adjusting one or more clocks and/or operatingvoltages used by the core. For example, one embodiment may use controllogic to enable or disable, voltage transformers, charge pumps, or someother voltage altering mechanism to control the voltage to one or moreportions of a processor or processing core. Alternatively orconjunctively, one embodiment may use control logic to enable or disableone or more phase lock loops (PLLs), clock dividers, or some other clockgating mechanism to control the frequency, phase, duration, etc., of oneor more clock signals used to operate one or more portions of aprocessor or processing core.

Moreover, power consumption of processing components, such as aprocessor or core, may be controlled according to a specification, sothat an operating system or other software or hardware may place thecomponent into one or more power states, such that the difference,ratio, or range of power consumption change may be known in relation toother power consumption states. One such specification is the ACPI powerspecification, which, among other things, may define a number ofcomponent power states (or “c states”) according to a range by whichpower consumed by the component is to change in relation to the othercomponent power states by placing the component in a particular powerstate. A component, such as a processing core, may be capable ofsupporting several ranges of power consumption defined by aspecification by adjusting the clocks, operating voltage, or both.

In the case of ACPI, for example, a processing core, according to oneembodiment, may support the ability to enter a “c3” state, in which theoperating voltage of a core or processor is reduced to the minimum levelrequired to retain state, rather than change output data, while theoperating voltage. In other embodiments, other power states may besupported by a processor and/or core, either included in the ACPIspecification or in some other specification.

At least one embodiment of the invention may place a processor orprocessing core into a particular power state (defined by ACPI orotherwise) without regard to and without first coordinating with anotherprocessor or core within the same system or die. Advantageously,embodiments of the invention may enjoy greater power controlflexibility, while reducing the time and/or logic necessary to change aprocessor or core power state, than in some of the prior art.

FIG. 1 illustrates a multi-core processor, in which at least oneembodiment of the invention may be used. Specifically, FIG. 1illustrates a processor 100 having processing cores 105 and 110integrated within the same die. In other embodiments, the cores may beon separate die or may be in separate processors. Furthermore,embodiments of the invention may also be applied to processors orsystems having more than two cores or processors. The exact arrangementor configuration of the cores in FIG. 1 are not important to embodimentsof the invention. In some embodiments, numerous cores may be arranged inother configurations, such as a ring. Located within each core of FIG. 1is a power controller to control the power consumed by the respectivecore. In other embodiments, each core's power may be controlled by logic(software, hardware, or both) located elsewhere, including outside ofthe processor.

Illustrated within the cores of FIG. 1 are pipeline stages forprocessing instructions. In other embodiments, other logic may be foundwithin the cores. In one embodiment, the cores are out-of-orderexecution cores, whereas in other embodiments, they may processinstructions in-order. Furthermore, in other embodiments, the cores maybe of different types with different logic located within.

FIG. 2 illustrates a processor core, in which at least one embodimentmay be used. The processor core 200 illustrated in FIG. 1 may includeone or more output circuits 207 to drive data onto one or more busesconnected to either or both cores, such that data can be delivered toother circuits, devices, or logic within the processor or outside of theprocessor. Also located within, or otherwise associated with, eachprocessor core of FIG. 1 is one or more power circuits 208 to reduce orincrease the operating voltage of one or more portions of the core, aswell as one or more clock modification circuits 209, such as one or morePLLs, to modify one or more clock signal frequencies, phases, workcycles, etc. In one embodiment, the one or more power circuits mayinclude a number of transistors to implement a voltage divide circuit.The power circuits may use other devices or circuits to reduce orincrease power to the cores, including charge pumps, voltage transformercircuits, etc.

In one embodiment, the core of FIG. 2 may have its power consumptionadjusted according to various power states through power control logic215. In one embodiment, the power control logic can respond to activitylevels of each core independently of one another to adjust the voltageand/or the clock(s) used by each core, without coordinating, orotherwise detecting, the power states of the other core(s). For example,in one embodiment, the power control logic may detect a change in thework load or activities, or receive a signal from a detection circuit todetect the change in work load or activity, of a corresponding core andadjust either the voltage (via the power circuits) or one or more clocks(via the clock modification circuits) or both to put the core into apower state that best matches the requirements of the activity level orload. Furthermore, in one embodiment, the control logic may change thevoltage and/or clock(s) of the core(s) in response to a thermal changein the core(s), or a change in the amount of current being drawn by thecore(s).

In one embodiment, for example, the power drawn by a core is reduced ifthe core is relatively idle for a period of time. In one embodiment, thepower is reduced in the core by placing the core in a c3 state or someother power state. Furthermore, in one embodiment the core is placedinto a new power state without first detecting the power state ofanother core in the processor or system, or otherwise coordinating thechange of power state with another core. Advantageously, at least oneembodiment may enable each core to respond to power conditions andrequirements on the core independently of other cores, such that eachcore may adjust its power consumption without regard to the power statesof other cores.

In addition to the core logic, other circuits may be included in theprocessor, such as “un-core” logic. The un-core logic may includecircuits to perform other functions besides those performed by the core,such as memory interface functions, digital signal processing functions,graphics functions, etc. In one embodiment, the power consumed by theun-core logic may be controlled in a similar manner as described inregard to the one or more cores. Furthermore, in some embodiments, inwhich the core and un-core logic have different voltage and/or clockingrequirements, the power consumed by the core and un-core logic may becontrolled independently of each other, just as the power consumed bythe cores may be controlled independently of each other.

FIG. 3 illustrates power control logic, according to one embodiment,which may place a core or un-core logic, and corresponding outputs, intoone of the power states discussed below. The power control logic 300includes at least one input 301 to detect at least one condition of acorresponding core or un-core logic. In one embodiment, the at least onecondition may be a prescribed period of relative inactivity of the coreor uncore, whereas in other embodiments, the condition may be aparticular level of power consumption or thermal condition of the coreor un-core logic. In other embodiments, other conditions or somecombination of conditions may be detected by the power control logic orsome other detection logic in order to indicate to the control logicwhether to place the corresponding core or un-core logic into adifferent power state.

Power control logic 300 also includes an output 310 to control one ormore PLLs responsible for delivering a clock signal to the correspondingcore or un-core logic. Furthermore, the power control logic 300 may alsoinclude an output to control a voltage modification logic or circuit,such as one using one or more power transistors, voltage divider, orvoltage transformation device. In other embodiments, the power controllogic may include more inputs and/or more or fewer outputs. Furthermore,in one embodiment, the power control logic may be located within thesame processor as the core it controls, whereas in other embodiments, itmay be located outside of a processor containing a core it controls. Inone embodiment, the power control logic may be implemented usinghardware circuits, whereas in other embodiments, the power control logicmay be implemented in software, or both hardware and software.

The power control logic may control the power of a core according to anynumber of logical operations, depending on the circumstances in which acore is to be power controlled. However, the power control logic may notrequire coordination with other control logic controlling the power ofother cores, such that the power control logic may control the power ofa core independently of the power state or power control of any othercore or processing element. Advantageously, the power control logic maycontrol the power consumption of a core (or number of cores) withoutdetecting a power state of another core, or otherwise coordinating withother cores, such that power control of each core may be performed moreefficiently than some prior art power control techniques.

FIG. 4 is a flow diagram illustrating operations that may be performedaccording to one embodiment. For example, at operation 401, powercontrol logic receives a signal to indicate some power-related conditionof a core being power controlled by the power control logic. If thesignal indicates a first condition at operation 405, the power controllogic may place a core or un-core logic into a first power state atoperation 407, such as an ACPI c3 state, whereas if a second conditionis indicated by the signal at operation 410, the power control logic mayplace the core or un-core logic into a second power state at operation413. In at least one embodiment, a number of cores may be powercontrolled according to at least the above operations independently ofeach other.

FIG. 5 illustrates a front-side-bus (FSB) computer system in which oneembodiment of the invention may be used. A processor 505 accesses datafrom a level one (L1) cache memory 510 and main memory 515. In otherembodiments of the invention, the cache memory may be a level two (L2)cache or other memory within a computer system memory hierarchy.Furthermore, in some embodiments, the computer system of FIG. 5 maycontain both a L1 cache and an L2 cache.

The main memory may be implemented in various memory sources, such asdynamic random-access memory (DRAM), a hard disk drive (HDD) 520, or amemory source located remotely from the computer system via networkinterface 530 containing various storage devices and technologies. Thecache memory may be located either within the processor or in closeproximity to the processor, such as on the processor's local bus 507.

Furthermore, the cache memory may contain relatively fast memory cells,such as a six-transistor (6T) cell, or other memory cell ofapproximately equal or faster access speed. The computer system of FIG.5 may be a point-to-point (PtP) network of bus agents, such asmicroprocessors, that communicate via bus signals dedicated to eachagent on the PtP network. FIG. 6 illustrates a computer system that isarranged in a point-to-point (PtP) configuration. In particular, FIG. 6shows a system where processors, memory, and input/output devices areinterconnected by a number of point-to-point interfaces.

The system of FIG. 6 may also include several processors, of which onlytwo, processors 670, 680 are shown for clarity. Processors 670, 680 mayeach include a local memory controller hub (MCH) 672, 682 to connectwith memory 22, 24. Processors 670, 680 may exchange data via apoint-to-point (PtP) interface 650 using PtP interface circuits 678,688. Processors 670, 680 may each exchange data with a chipset 690 viaindividual PtP interfaces 652, 654 using point to point interfacecircuits 676, 694, 686, 698. Chipset 690 may also exchange data with ahigh-performance graphics circuit 638 via a high-performance graphicsinterface 639. Embodiments of the invention may be located within anyprocessor having any number of processing cores, or within each of thePtP bus agents of FIG. 6.

Other embodiments of the invention, however, may exist in othercircuits, logic units, or devices within the system of FIG. 6.Furthermore, in other embodiments of the invention may be distributedthroughout several circuits, logic units, or devices illustrated in FIG.6.

Processors referred to herein, or any other component designed accordingto an embodiment of the present invention, may be designed in variousstages, from creation to simulation to fabrication. Data representing adesign may represent the design in a number of manners. First, as isuseful in simulations, the hardware may be represented using a hardwaredescription language or another functional description language.Additionally or alternatively, a circuit level model with logic and/ortransistor gates may be produced at some stages of the design process.Furthermore, most designs, at some stage, reach a level where they maybe modeled with data representing the physical placement of variousdevices. In the case where conventional semiconductor fabricationtechniques are used, the data representing the device placement modelmay be the data specifying the presence or absence of various featureson different mask layers for masks used to produce an integratedcircuit.

In any representation of the design, the data may be stored in any formof a machine-readable medium. An optical or electrical wave modulated orotherwise generated to transmit such information, a memory, or amagnetic or optical storage medium, such as a disc, may be themachine-readable medium. Any of these mediums may “carry” or “indicate”the design, or other information used in an embodiment of the presentinvention, such as the instructions in an error recovery routine. Whenan electrical carrier wave indicating or carrying the information istransmitted, to the extent that copying, buffering, or re-transmissionof the electrical signal is performed, a new copy is made. Thus, theactions of a communication provider or a network provider may be makingcopies of an article, e.g., a carrier wave, embodying techniques of thepresent invention.

Thus, techniques for steering memory accesses, such as loads or storesare disclosed. While certain embodiments have been described, and shownin the accompanying drawings, it is to be understood that suchembodiments are merely illustrative of and not restrictive on the broadinvention, and that this invention not be limited to the specificconstructions and arrangements shown and described, since various othermodifications may occur to those ordinarily skilled in the art uponstudying this disclosure. In an area of technology such as this, wheregrowth is fast and further advancements are not easily foreseen, thedisclosed embodiments may be readily modifiable in arrangement anddetail as facilitated by enabling technological advancements withoutdeparting from the principles of the present disclosure or the scope ofthe accompanying claims.

Various aspects of one or more embodiments of the invention may bedescribed, discussed, or otherwise referred to in an advertisement for aprocessor or computer system in which one or more embodiments of theinvention may be used. Such advertisements may include, but are notlimited to news print, magazines, billboards, or other paper orotherwise tangible media. In particular, various aspects of one or moreembodiments of the invention may be advertised on the internet viawebsites, “pop-up” advertisements, or other web-based media, whether ornot a server hosting the program to generate the website or pop-up islocated in the United States of America or its territories.

1. A processor comprising: a first processing core comprising a firstinstruction decoder, a first reorder buffer, and a first plurality ofexecution units; a second processing core comprising a secondinstruction decoder, a second reorder buffer, and a second plurality ofexecution units; and a power control logic to be controlled by softwareto independently adjust a clock frequency of both of the first andsecond processing cores respectively based on a workload of the firstand second processing cores, wherein the power control logic is toindependently adjust the clock frequency of both of the first and secondprocessing cores by controlling a frequency of a clock signalrespectively generated by a first and second phase-lock loop (PLL)circuit.
 2. The processor of claim 1 further comprises a clock divider,wherein the clock divider to decrease the clock frequency of the clocksignal respectively generated by the first and second phase-lock loop(PLL) circuit in response to a decrease in the workload of the first orthe second processing cores.
 3. The processor of claim 1, wherein thepower control logic is to cause the frequency of the clock generated bythe first PLL circuit to be divided in response to a change in workloadof the first processing core, wherein the first PLL circuit is coupledto the first processing core.
 4. The processor of claim 3, wherein thepower control logic to cause the frequency of the clock generated by thefirst PLL circuit to be divided in response to a decrease in theworkload of the first processing core.
 5. The processor of claim 1,wherein the power control logic is to cause the frequency of the clockgenerated by the second PLL circuit to be divided in response to adecrease in the workload of the second processing core independently ofthe change in the workload of the first processing core, wherein thesecond PLL circuit is coupled to the second processing core.
 6. Theprocessor of claim 3, wherein the power control logic to cause thefrequency of a plurality of clocks generated by the first PLL circuit tobe divided in response to a decrease in the workload of the firstprocessing core.